1. Field of the Invention
The present invention relates to a toner that is used in electrophotographic systems, electrostatic recording systems, and toner jet recording systems. More particularly, the present invention relates to a toner for use in copiers, printers and facsimile machines that produce a fixed image by forming a toner image on an electrostatic latent image bearing member, thereafter forming a toner image by transfer the toner image to a transfer material, and fixing the toner image by the application of heat and pressure.
2. Description of the Related Art
With the growth in worldwide demand for copiers and printers in recent years, there has been desire for copiers and printers that can be used in a wide variety of environments.
Heavy users require a high durability without a decline in image quality even at large numbers of copies or prints. Small offices and households, on the other hand, require the consistent production of high-quality images with no influence from the use environment, particularly, the temperature and humidity.
As a consequence, of course a high durability and also a humidity-independent charging performance are required of the toner.
Organopolysiloxanes are known to be materials that exhibit a low interfacial tension. It can therefore be expected that the introduction of an organopolysiloxane structure into the surface region of toner would provide a humidity-independent charging performance, and various investigations in this regard have also been carried out to date.
Organopolysiloxanes, on the other hand, typically have a glass transition temperature (Tg) below room temperature, and thus, when present in large amounts in a toner, the toner softens and the durability readily deteriorates. In addition, the adhesiveness between the melted toner and paper is reduced and the toner readily separates from the fixed image. As a consequence, the additive amount of organopolysiloxane and the state in which it is present must be controlled.
Japanese Patent Application Laid-open No. 2010-132851 discloses a toner with a core-shell structure that contains an organopolysiloxane compound as a binder resin. This art provides an excellent releasability of the toner from the heat-fixing roll and yields an image that is stable on a long-term basis. However, this art uses the organopolysiloxane compound not only for the shell, but also as the core material, and as a consequence the toner has an overly large content of the organopolysiloxane structure. This has resulted in the problem of facile separation of the toner from the fixed image.
Japanese Patent Application Laid-open No. 2010-132851 discloses an example in the realm of resin particle production in which resin particles are obtained by using supercritical carbon dioxide or a fluid that is a nonaqueous medium as a dispersion medium and using a compound having an organopolysiloxane structure as a dispersion stabilizer. It was found, however, that this art does not provide a stability in a variety of environments, because the compound having an organopolysiloxane structure is used in the form of a solution in this art, a structure in which this compound remains at the surface of the resulting resin particles does not occur.
With respect to resin particle production in the aforementioned dispersion medium, Japanese Patent Application Laid-open No. 2010-168522 describes an example in which a compound containing an organopolysiloxane structure is used as a toner shell material. However, the organopolysiloxane structure is present in a large proportion in the organopolysiloxane compound in this art, and as a consequence it was found that the toner surface is susceptible to soften and the durability readily declines as a result.
Another method that can be contemplated is the external addition of an organopolysiloxane compound to the toner particles. In this case, however, liberation of the organopolysiloxane compound from the toner particle and burying in the toner particle occur during continuous image output and it is therefore difficult to obtain stable images over a long term.
As described above, in a toner containing an organopolysiloxane compound, problems still remain in achieving a better balance between the stability in a variety of environments and the durability and fixed image stability.